core::Manager::stop() should make sure ongoing hash checks get cleaned
up.

Polling during last phase of shutdown should be very quick, don't use
normal timeout.

Make clear distinction of upload/download throttle.

Consider basing WindowPeer* on a common base class.

Some kind of indication that a tracker request was tried, but won't be
allowed since the tracker set a min interval.

Make accumulate return the value, no refs please...

!!! Clean up logs at regular intervals.